1. Field of the Invention
The present invention relates to apparatus and methods for testing welds and, more particularly, for testing welds on nozzles or other such fixtures.
2. Description of the Prior Art
In chemical or petrochemical plants etc., it is often necessary to convey fluidic materials from one location, or holding cell to another. The conveyance of such material normally includes equipment such as conduits or pipes, storage or reaction vessels etc., which are generally manufactured from metal. The joining of separate pieces of the conveying equipment is generally achieved by welding the necessary pieces together. For example, when joining adjacent ends of pipe together, it is common for each end to be provided with flanges, welded to each respective end, which are then bolted together to form a seal. Alternatively, the ends of pipes or other equipment may be welded directly together for form the necessary conduit. In either case, it will be appreciated that each welded joint must form a complete seal so as to prevent leakage of the materials being transported. This is particularly the case when handling potentially hazardous (i.e. flammable) or toxic materials.
For reasons of safety, it is often necessary to periodically test the integrity of the welds used in joining the various pieces of equipment (such as pipes, vessels, flanges and the like) together. However, a particular problem is encountered when attempting to test the integrity of welds used in joining a nozzle to a pipe or vessel. Nozzles generally comprise a short conduit with one end inserted into or abutting an opening in a pipe or vessel and an opposite end having a flange. The joints between the conduit portion of the nozzle and the pipe or vessel and the flange, respectively, are sealed with welds. As is known in the art, nozzles can range in size from less than an inch to up to several feet in diameter.
The prior art teaches various tools for conducting weld integrity tests on conduits. For example, U.S. Pat. Nos. 6,131,441 and 5,844,127 (Berube and Carson) (the entire disclosures of which are incorporated herein by reference) teach weld testing tools which isolate a particular section of a pipe (for example, a section including a weld) and subject the section to a high pressure fluid within a constrained annular space defined by the tool and the inner surface of the pipe. The pressure of the fluid within the annular space is monitored whereby any pressure drop signifies a leak in the weld.
U.S. Pat. No. 5,024,079 (Dufort) teaches a tool for testing welds on flanged pipes. The tool includes a first piece that is inserted into the flange and which extends partially into the length of the pipe. The first piece is sealed against the pipe wall. A second piece of the tool is positioned outside of the pipe and bears against the flange opening. The two pieces are connected together by a shank, which extends axially through pipe and is of a much smaller diameter than the pipe. This arrangement creates an annular space which is filled with a pressurized fluid. This reference does not teach a tool that can be used for a nozzle provided on a vessel. Further, since the tool must be sized with respect to the diameter of the pipe being tested, the resulting weight of a tool for large diameter equipment renders the tool very difficult to install and use.
U.S. Pat. No. 6,367,313 (Lubyk) teaches another test tool, or plug, for testing the integrity of welds in a pipe. The tool of this reference is designed to be adjustable to various diameters of pipes but still includes a structure that is similar to that of U.S. Pat. No. 5,024,079 discussed above. This reference also does not teach a tool that can be used on a vessel nozzle and includes the same deficiency of increased weight mentioned above in that a tool for larger diameter pipes
U.S. Pat. No. 6,463,791 (Berube and Carson) (the entire disclosure of which is incorporated herein by reference), however, does teach an apparatus for testing welds used to secure nozzles. As shown in FIG. 1 of this reference, the apparatus comprises a first seal plate that is placed on the inner surface of the vessel (for example) and a second seal plate that is secured to the outer, flange portion of the nozzle. In this manner, the nozzle volume is sealed and a pressurizing fluid is introduced therein. Once the volume is filled, the pressure is monitored as above and any leakage detected. Although this apparatus provides an accurate and efficient means of testing welds on nozzles, the size and weight of the apparatus makes it inconvenient for use on large nozzles.
Further, as will be understood, a testing apparatus, particularly those of larger sizes, requires at least two technicians to properly position the apparatus and to conduct the test. In this case, at least one technician will be located within the vessel, on the inside end of a nozzle, and at least one other technician will be located outside of the vessel, at the flange end of the nozzle. Thus, it is often necessary to provide a means of communication between the technicians to properly co-ordinate the test. Although the nozzle opening itself is one means of communication, many of the prior art apparatus, as discussed above, completely seal the nozzle opening thereby preventing communication there-through. It will be understood that electronic communication devices cannot be used in most cases where flammable vapour residues and the like may exist. Further, by sealing off the larger nozzle openings, the prior art devices also block the quickest means of ingress and egress for the technicians, which could pose a safety hazard.
Thus, a testing tool for nozzles is desired that overcomes some of the deficiencies associated with prior art apparatus.